In response to growing market demand for light weight and high performance products, hardware and software for portable equipments such as video cameras, mobile phones, digital cameras, and the like, are dramatically being developed, and combined with this dramatic development, many studies are being made on a secondary battery as a power source for operating such equipment.
A secondary battery is not only commonly applied to portable equipments, but universally applied to an electric vehicle (EV) or a hybrid vehicle (HV) that is propelled by an electric motor.
A secondary battery for use in vehicles is gaining attention for its primary advantage of remarkably reducing the use of fossil fuels and not generating by-products from the use of energy, making it a new eco-friendly source of energy.
Generally, a battery (pack) for use in electric vehicles is implemented as an assembly consisting of a plurality of unit cells and a plurality of such assemblies, and the cell has a structure of being chargeable and dischargeable by an electrochemical reaction between elements including a cathode current collector, a separator, an active material, an electrolyte solution, an aluminum thin-film layer, and the like.
In addition to this basic structure for charging and discharging, the battery further includes a device for physical protection when cells are assembled into a battery, various sensing means, firmware with an accurate algorithm for state of charge (SOC) estimation, and the like.
Due to intrinsic characteristics of an electrochemical reaction occurring inside, the use of the battery made up of various chemical devices and electrical and physical devices is impermanent. Furthermore, due to these electrochemical reactions and the like, leakage current and the like may occur, which fails to ensure safety and so remains as one of the problems to be solved.
The intrinsic electrochemical or electrical and physical characteristics of the battery are unavoidably influenced by an external environment in which the battery is used, and the intrinsic electrochemical characteristics of the battery may suddenly change based on the external environment to which the battery is exposed, which thereby affects the life, safety or operation performance of the battery.
That is, the battery has an intrinsic attribute in that its electrical and physical characteristics degrade over time, and is sensitively influenced by its environment, for example, an external unfavorable condition such as temperature, a high current environment, a physical impact, overcharge, overdischarge, submergence, overmoisture, and the like. The longer the battery is exposed to this situation, the more it will decrease in battery life, which cannot guarantee that the battery will run within its optimal period, and since there are risks of explosion, this may become a fatal factor in threatening the safety of a car to which the battery is applied.
Therefore, there is a great need for improvement in user interfacing environment to control the management of a battery in consideration of various external environmental factors so as to maximize the stable management and normal operation of the battery and optimize the economical efficiency of the battery, and to take prompt or preliminary action when the battery is exposed to a dangerous level.
Also, medium- and long-term exposure of the battery to the above-mentioned unfavorable condition gradually increases a so-called fatigue of the secondary battery and deteriorates the electrochemical, electrical, and physical characteristics, leading to increased rates of battery degradation, which limits the time of normal operation, causing a reduction in the battery life.